


live a little

by jouska



Category: Fate/Zero, Fate/stay night & Related Fandoms
Genre: Anal Fingering, Anal Sex, Begging, Birthday Sex, Blow Jobs, Established Relationship, Floor Sex, Fluff and Smut, M/M, Multiple Orgasms, Teasing
Language: English
Status: Completed
Published: 2019-11-13
Updated: 2019-11-13
Packaged: 2021-01-29 18:49:49
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,817
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21414958
Author URL: https://archiveofourown.org/users/jouska/pseuds/jouska
Summary: Kiritsugu doesn't make a habit of remembering when his birthday is. If it weren't for the kids, he wouldn't even celebrate it. Kariya takes a bit of issue with that, wanting to show Kiritsugu that there's plenty worth celebrating.
Relationships: Emiya Kiritsugu/Kariya Matou
Comments: 2
Kudos: 28





	live a little

**Author's Note:**

  * For [lufiia](https://archiveofourown.org/users/lufiia/gifts).

> (mfw i'm clocking in at 7k for the next chapter of absolution and i'm STILL not done)
> 
> my buddy larsa commissioned me to give kiritsugu a lovely and good birthday time in that little "kariya and kiritsugu are alive and boyfriends in between f/z and fsn" au! i'm a day late but happy birthday, kiritsugu

“Kariya,” Kiritsugu mutters, his voice strained. “Can’t this wait until we get—to the bedroom—”

Looking up at him through his bangs, Kariya smiles, tilting his head a little. “No, why? Come on, we’ve done it in more open places, what’s the problem?”

“Y—You don’t have to say it like that,” Kiritsugu bites his lip, his feet scraping against the tatami. “Makes it sound like we’re a couple of perverts or something.”

Kiritsugu has plenty of reasons to be worried—the kids are just down the hall, they’re still excited from celebrating Kiritsugu’s birthday (a party he didn’t really want, but enjoyed nonetheless), they might wake up thirsty and want a drink. And yet here he is, splayed out on his back, his yukata pulled open, with Kariya crouched between his legs.

“Think of it this way, then,” Kariya lathes his tongue over the front of Kiritsugu’s boxers, kneading at his cock through the thin material. “Next time, remember to _warn_ me that your birthday’s coming up. If I knew beforehand, I would’ve booked us at a hotel or something.”

Chest heaving, Kiritsugu tips his head back, biting the inside of his cheek. He can’t make a sound, he doesn’t want any of the kids walking in on this, but Kariya is too _good_ at teasing him; despite his best efforts, a deep groan works up from his chest, muffling through his pursed lips. “I told you I’m sorry, I—ahhh, _fuck_—I don’t make it a habit, remembering stuff like that…”

Kariya kisses him through his boxers again, his thumb teasing the base of his cock. It takes all of Kiritsugu’s self control to keep himself from swearing out loud, which just makes Kariya laugh. “Well you _should._ I would’ve set us up really nice, the kids could’ve had their own room, I could’ve gotten us a really nice lover’s suite, we could’ve sat in a hot tub, maybe make out a little, stuff like that.”

Huffing through his nose, Kiritsugu tips his chin down against his collarbone, regarding Kariya with wide eyes. “You… you don’t have to do stuff like that for me.”

Puffing his cheeks out, Kariya gives one rough stroke to his cock, thumbing the head through the dampened fabric. Kiritsugu’s legs kick out involuntarily, his hips jumping up as he claps both of his hands over his mouth to muffle the startled squeal he almost lets out. Kariya keeps stroking him through his underwear, biting at his thighs as he sighs, “You’re totally missing the point.”

He wants to tell Kariya to stop, but the longer he touches him, the more he just wants Kariya to rip his boxers off and suck him off already, _please, please god, I can’t hold my voice back much longer. _But Kariya doesn’t, he just continues sucking at the soft give of Kiritsugu’s inner thighs, biting at the junction where his hip meets his thigh.

“Kariya, _fuck,_” Kiritsugu hisses through his hands, thighs squeezing around him. “Please—”

“Hmmm?” Kariya lifts his head, resting his cheek against Kiritsugu’s cock. He’s grinning like he _isn’t_ edging Kiritsugu to the point of tears, like his lips aren’t smeared with spit and precum. “Please what?”

“Please… _fuck,_” Kiritsugu slides his hands up to cover his eyes, hating how broken apart he sounds. “Fuck me… god, _please_ fuck me.”

“Aw, how can I say no to that?” Kariya kisses at Kiritsugu’s cockhead, finally shifting his hand to pull his boxers off. “Anything for the birthday boy.”

The way Kariya says that, his tone low but dripping with fondness, makes Kiritsugu sob out loud. He lifts his hips up, all but kicking his boxers across the room once they’re worked down his one leg. There’s a wet smack against the paper door, and Kiritsugu feels his ears burning. _Shit, how am I going to explain that tomorrow?_

Before he can worry himself sick over it, Kariya is closing his lips around Kiritsugu’s prick, and all otherwise coherent thoughts are melting right out of his ears in favor of _holy shit, holy shit, holy shit, finally._ Kiritsugu whimpers, tossing his head to the side as Kariya sucks and tongues at the head, his hand loosely jerking at what he can’t fit in his mouth.

He doesn’t last long—he never does when Kariya uses his mouth. Kariya moans around him, taking in more and more of Kiritsugu’s cock with each pass. Shaking, Kiritsugu weaves one hand into Kariya’s hair, hips helplessly bucking up into his face. He knows Kariya likes this—when Kiritsugu gets close, he likes it when he loses control a little, likes it when Kiritsugu fists his hair and pushes up and into Kariya’s mouth, fucking down his throat in arrhythmic, shaky thrusts until—_until—_

“Ah, _ahh, hahh, Kariya—fuck!”_ Kiritsugu can’t hold down his voice, letting out a cry as he cums hard down Kariya’s throat. Kariya hums around him, his hand rubbing soothing circles into Kiritsugu’s bare hip as he swallows. His throat squeezes around Kiritsugu’s cock, sending pleasant little shocks through his system.

As Kariya pulls off him, Kiritsugu whimpers, one of his legs curling around Kariya’s crouched form. Kariya laughs as he sits upright, licking his lips. He reaches out, trailing his fingers lightly along Kiritsugu’s heaving chest. “You’re so good for me. Think you can handle a little more? Getting you all flushed and pretty like this, it’d be mean of me _not_ to.”

Kiritsugu just nods frantically, lifting his hips up. Kariya smiles, spreading his legs out. He takes a moment to pull a bottle of lube out of his obi—_he still hasn’t gotten naked, he’s still in his yukata, god, please get naked, I wanna see you—_before he loosens it, letting it slide off. Shrugging the yukata off his shoulders, Kariya leans forward, pressing the lube into Kiritsugu’s hand. “Help me?”

Though Kariya is more than capable of stretching him open, Kiritsugu finds that he likes to watch him finger himself. He isn’t complaining—if Kariya’s happy, he’s happy. Fumbling with the bottle of lube, Kiritsugu squeezes a healthy amount onto his fingers, reaching down between his legs and prodding at his entrance. While he does that, Kariya leans over, pressing his lips against the corner of Kiritsugu’s mouth, tongue sliding against his bottom lip.

“Didn’t you say you were a virgin before we met?” Kiritsugu pants, working one finger into himself up to the knuckle. He’s impatient, so he’s rushing it a bit, thrusting his finger in and out before adding a second. “You don’t act like any virgin I’ve ever met.”

Kariya kisses him on the cheek. As chaste as that is, Kiritsugu can feel him grinding his erection against his stomach, his cock drooling long lines of precum against his skin. “It’s true, I was. But god, when I’m around you, it’s like I’m a horny teenager all over again.”

Working in another finger, Kiritsugu gulps, his eyes sliding shut. “You’re not just… mm, buttering me up because it’s my birthday?”

“Of course not,” Kariya whispers against his cheek, sounding more than a little breathless himself. “I think about you all the time, you know.”

Slipping in a third finger, Kiritsugu lets a moan slip, cracking one eye open. He’s all but fucking himself on his fingers now, gauging Kariya’s reaction as he goes faster. He can see the slow bob of his Adam’s apple now, can feel Kariya’s cock throb against his hip. Kiritsugu grinds up against it a little, smiling innocently when Kariya swears under his breath.

“I… I think about you, too…” Kiritsugu breathes, letting out a hum when he presses his fingers against his prostate. His cock swells all over again, and he _knows_ Kariya can feel it. “All the time…”

“Jesus,” Kariya huffs as he sits back up, scooting back and grabbing at Kiritsugu’s wrist. “I’m supposed to be the one teasing _you._”

“Sorry, sorry,” Kiritsugu pulls his fingers out of himself, squeezing some lubricant into Kariya’s expectant hand. He watches Kariya slick himself up, his own hand trailing down to jerk himself off. “I couldn’t help it. I’m not as good of a tease as you, though.”

“Damn right,” Kariya grunts, urging Kiritsugu’s left leg up onto his shoulder. He nudges his cock against Kiritsugu’s asshole, hissing out a tense breath as he presses into him. “You’ll have to talk more like that for me on _my_ birthday.”

“You’ll—_ahh,_” Kiritsugu tips his head back, squeezing the base of his own cock. “H-Have to give me a few pointers.”

“Only if you call me _sensei,_” Kariya groans, twitching. “Kariya-sensei sounds pretty hot, doesn’t it?”

“God, it _does,_” Kiritsugu grits his teeth, forcing himself to breathe evenly as Kariya’s cock slowly fills him up. “_Fuck._”

Kariya grips tightly at Kiritsugu’s thigh as he slides in deep, seating himself fully inside. Neither of them have the necessary oxygen in their brains to continue bantering; Kariya is shaking, tipping forward, sweat dripping from his chin. Kiritsugu can barely breathe, feeling full, _so_ full, it aches, but he doesn’t want Kariya to pull out, doesn’t want him to leave.

He does move, though, after a minute or so. He slowly pulls out halfway, and then drives back in—Kariya isn’t rough, never is, but he’s _firm._ He’s deliberate with his thrusts, only ever pulling out halfway, intent on pleasing Kiritsugu with every move he makes.

“Kariya,” Kiritsugu whimpers, his hand stuttering over his own cock. It’s too nice, it’s not enough, he wants more. “_Please._”

Instead of answering verbally, Kariya picks up the pace of his thrusts, fucking into Kiritsugu hard and _deep,_ pressing in firmly once Kiritsugu lets out a sharp cry—_“Holy fuck,_ there, right there, harder, _fuck,” _Kiritsugu feels himself cumming again, spurting onto his chest and up to his chin.

“So cute,” Kariya purrs, rolling his hips with his next thrust. “Fuck, you’re so cute—_hahh,_ I’m close, holy _fuck_ am I close—”

Letting his leg fall off Kariya’s shoulder, he reaches up, clawing, dragging Kariya down on top of him so he can kiss him. He’s not good at kissing, they both know he isn’t, but Kariya is there, licking into his mouth, pinning his hips hard against Kiritsugu’s ass. Kariya cums like that, with Kiritsugu’s arms wrapped around him, clinging to him tightly.

“So hot,” Kariya pulls his tongue out of Kiritsugu’s mouth, murmuring against his lips. “Fuck, you’re so hot.”

“Don’t pull out yet,” Kiritsugu’s floating, his tongue a little looser, a little less anxious about what he says around Kariya in his fucked-out state. “Nngh. Think I like being called hot more than being called cute.”

Obediently, Kariya stays where he is, sweat-slicked skin sticking against Kiritsugu’s. “But you _are_ cute.”

“Nuh-uh, I can’t. I’m… I’m, uh…” Kiritsugu tries to think. “Fuck, how old am I again?”

Kariya laughs, pressing his forehead against his. “You’re so weird.”

**Author's Note:**

> check me out at diokyouran on tumblr, and @suspiciouslyjo on twitter!


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